Non-alcoholic fatty liver disease (NAFLD) is a representative liver disease that causes liver inflammation and damage. When aggravated, NAFLD develops into non-alcoholic steatohepatitis (NAS) with symptoms such as cirrhosis and fibrosis. According to recent reports, it has been known that peroxisome proliferator activated receptor (PPAR)γ2 as a transcriptional factor is overexpressed and activated in the liver of fatty liver patients. In addition, the activation of PPARγ2 induces the expression of a variety of target proteins involved in lipid metabolism of the liver. Proteins, so-called 14-3-3, involved in the activity of such a transcriptional factor exist as seven isoforms (α/β, ε, η, γ, τ/θ, δ/ζ; and σ). 14-3-3 proteins are known to bind to the phosphorylation site of a transcriptional factor and regulate the activity of the transcriptional factor, and are also involved in regulating metabolism-associated transcriptional factors. Thus, the inventors of the present invention investigated the role of 14-3-3 proteins in the onset and regulation of fatty liver and, as a result, verified that 14-3-3β and 14-3-3γ, which are regulating factors, are proteins that play a vital role in lipid metabolism, and can be used as a target for the treatment of non-alcoholic fatty liver, thus completing the present invention.